It is often desired to search, for playback, a desired part of a video application composed of a large amount of different video data, such as a television program recorded in a video recorder, for example.
As a typical one of the image extraction techniques to extract a desired visual content, there has been proposed a story board which is a panel formed from a sequence of images defining a main scene in a video application. Namely, a story board is prepared by decomposing a video data into so-called shots and displaying representative images of the respective shots. Most of the image extraction techniques are to automatically detect and extract shots from a video data as disclosed in “G Ahanger and T. D. C. Little: A Survey of Technologies for Parsing and Indexing Digital Video, Journal of Visual Communication and Image Representation 7: 28-4, 1996”, for example.
It should be noted that a typical half-hour TV program for example contains hundreds of shots. Therefore, with the above conventional image extraction technique of G. Ahanger and T. D. C. Little, the user has to examine a story board having listed therein enormous shots having been extracted. Understanding of such a story board will be a great burden to the user. Also, a dialogue scene in which for example two persons are talking will be considered here. In the dialogue, the two persons are alternately shot by a camera each time either of them speaks. Therefore, many of such shots extracted by the conventional image extraction technique are redundant. The shots contain many useless information since they are at too low level as objects from which a video structure is to be extracted. Thus, with the conventional video structure extraction technique, the users cannot easily extract such shots.
That is to say, for the user's convenience in the video structure extraction, the conventional video structure extraction technique should be adapted to capture video structures at different levels including higher levels than the shots in accordance with the content of a video data. However, such a video structure extraction is very complex, so that an apparatus intended for extraction of such video structures should have a high capability of data processing and a large volume of computation resources. Thus, because of great costs and labor which would be required for such resources and data processing jobs, it is very difficult to implement such a function of video structure extraction in home video appliances.